Field of the Invention
The present invention relates to a weight measurement apparatus, a biological measurement apparatus, and a weight measurement program, for measuring a weight, based on a difference between an output in a state where an object to be measured is loaded on a placing unit and an output in a state where an object to be measured is not loaded on the placing unit.
Related Art
There exists a step-on type weight scale which can measure simply by a user stepping on the placing unit without the user operating a switch for consciously starting measurement.
This conventional step-on type weight scale updates a zero point at predetermined time intervals during nonuse, to acquire as correctly as possible the zero point as an output value in the state where the object is not put on the placing unit. A weight value calculated based on the difference is referred to as a measurement result. This difference is between the output value in the state where the object has stepped on the placing unit and the last updated zero point.
For example, the following step-on type weight scale is disclosed.
The step-on type weight scale of JP 4940026 B is to update the zero point when it is assumed that the zero point is not changed, in a placement state suitable for updating the zero point, at predetermined time intervals. A step-on type weight measurement apparatus of JP 2000-68984 A is to update the zero point at predetermined (updating) time intervals, and is to change the updating time interval of the next zero point, in accordance with a difference between a zero point at the last updated time and a zero point at this updated time.
Not just the step-on type weight scale, there also exists a weight scale which performs measurement by a user operating a switch for consciously starting the measurement. Even this switch-operation type weight scale updates the zero point at predetermined time intervals during nonuse.
However, in the conventional step-on type weight scale or the switch-operation type weight scale, the zero point is not necessarily updated right before an object to be measured is put on a placing unit. Thus, when the measurement environment (placement angle or temperature) has been changed, after the zero point has been acquired at last, during the time since the object to be measured has stepped on the placing unit until the measurement, an incorrect effect is somehow produced on the weight value as a measurement result. At this time, when calculating a correct measurement result, the measurement is necessarily performed, thus requiring procedures for that.